High purity iron, method of manufacturing thereof, and high purity iron targets

ABSTRACT

High purity iron with a very few content of impurities such as copper, a method of manufacturing thereof, and high purity iron targets are provided. The iron containing impurities such as copper is dissolved in a hydrochloric acid solution, and the concentration of the hydrochloric acid of the aqueous solution of iron chloride is adjusted to 0.1 kmol/m 3  to 6 kmol/m 3 . Then, iron is added in the aqueous solution of iron chloride, and an inert gas is injected into the solution with agitating, in order to convert the trivalent iron ions and divalent copper ions contained in the aqueous solution of iron chloride respectively to divalent iron ions and monovalent copper ions. Then, the aqueous solution of iron chloride is fed into a column filled up with the anion exchange resins. The divalent iron ions are not absorbed on the anion exchange resins although the monovalent copper ions are absorbed on the anion exchange resins. Therefore, copper can be separated from the aqueous solution of iron chloride. And then, the aqueous solution of iron chloride is evaporated to dryness, oxidized and heated in a hydrogen atmosphere to generate iron.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to high purity iron in whichcontents of impurities such as copper are reduced, a method ofmanufacturing thereof, and high purity iron targets.

[0003] 2. Description of the Related Art

[0004] Semiconductor devices such as VLSI (very large scale integratedcircuit) and ULSI (ultra LSI) have a structure where various thin metalfilms are deposited on, for example, a silicon (Si) wafer. Although theidea of using iron (Fe) as a material of magnetic random access memory(MRAM) has been considered in recent years, the accompanying injuriousimpurities in the iron may result in malfunction or deterioration of thesemiconductor device, which is undesirable. For example, copper (Cu) maycause a short circuit because of high diffusion rate inside silicon, andradioactive elements such as uranium (U) and thorium (Th) will causeincorrect operations, and alkaline metals and alkaline-earth metals maycause degradation of the device properties.

[0005] Furthermore, environmental semiconductor materials such as ironsilicide (FeSi₂) have been proposed in order to build new technologiesdealing with future problems in environment and depletion of resources.Iron silicide as an environmental semiconductor material requires as fewimpurities as typical compound semiconductors such as gallium arsenide(GaAs), cadmium telluride (CdTe) and so on. The upper limit of impuritycontent in iron silicide is less than in substances of semiconductordevices of VLSI and ULSI. Small amounts of impurities form impuritylevel that causes degradation of the semiconductor properties. Thus,iron as a semiconductor material needs high purity.

[0006] While levels in purity of the crude iron traded globally andpresently are about 98% to 99.8%, such crude iron contains variousimpurities, for example, transition metals such as nickel (Ni), cobalt(Co), and chromium (Cr), gas elements such as oxygen (O), nitrogen (N),and sulfur (S). Therefore, in order to use iron as materials ofsemiconductor devices and environment semiconductors, it is necessary toremove these impurities from the crude iron and achieve higherpurification. Moreover, iron appears favorable as materials of devicessuch as magnetic recording mediums and magnetic recording heads, as wellas semiconductor devices, because of bearing properties typical offerromagnetic metals. A higher purification of iron is indispensable tothe use of iron as materials of these devices.

[0007] Various methods of removing impurities from crude iron, forexample, wet processing such as solvent extraction, ion exchange, andelectrolytic refining for separation of metallic elements, and drynesshydrogen gas (H₂) processing for removal of gas elements such as oxygenand nitrogen, and floating zone melting refining method, have beenstudied.

SUMMARY OF THE INVENTION

[0008] However, there is a problem with the solvent extraction. It isdifficult to control extraction and reverse extraction and to refineiron surely in industrial processes. And, although nearly all of metalimpurities can be separated by the ion exchange, copper contents beforeand after refining by the ion exchange may not change, that is, it isdifficult to remove copper, which is a problem with the ion exchange. Inaddition, there are problems with the electrolytic refining that pHcontrol of electrolytic solutions is required, and it is difficult toremove nickel and copper. The floating zone melting refining method isintended to further raise the purity levels of metals purified to someextent, and in practice, it is reported that the floating zone meltingrefining method has large effects on purification (Yukio Ishikawa, KojiMimura, Minoru Isshiki, Bulletin of the Institute for Advanced MaterialsProcessing Tohoku University 51 (1995), pp.10-18). However, it isdifficult to apply the floating zone melting refining method to largescale and the method may not always produce high purity metals surely,that is, it is difficult to produce a large amount of high purity ironat a low price with the floating zone melting refining method.Therefore, a need exists for methods of purifying iron easily, surely,and highly, and particularly for the development of methods of removingcopper.

[0009] The present invention has been achieved in view of the aboveproblems. It is an object of the invention to provide high purity ironand high purity iron targets in which contents of impurities such ascopper are reduced.

[0010] It is another object of the invention to provide a method ofeasily and surely manufacturing high purity iron.

[0011] The invention provides high purity iron with 99.99 mass % or morein purity wherein a copper impurity content is 50 mass ppb or less.

[0012] In another aspect, the invention provides high purity ironwherein a residual resistivity ratio thereof is 3000 or more, and acopper impurity content is 50 mass ppb or less.

[0013] A method of manufacturing high purity iron according to theinvention comprises the steps of; converting trivalent iron ions andimpurity divalent copper ions contained in an aqueous solution of ironchloride respectively to divalent iron ions and monovalent copper ions;adjusting a concentration of hydrochloric acid in a range of 0.1 kmol/m³to 6 kmol/m³; and separating the monovalent copper ions from the aqueoussolution of iron chloride by using the ion exchange resins.

[0014] In another aspect, a method of manufacturing high purity ironaccording to the invention comprises: converting trivalent iron ions inan aqueous solution of iron chloride to divalent iron ions; adjusting aconcentration of hydrochloric acid in a range of 0.1 kmol/m³ to 6kmol/m³; and separating impurities of at least one selected from thegroup consisting of zinc, gallium, niobium, technetium, ruthenium,rhodium, palladium, silver, cadmium, indium, tin, antimony, tellurium,tantalum, tungsten, rbenium, osmium, iridium, platinum, gold, mercury,thallium, lead, and bismuth from the aqueous solution of iron chlorideby using the anion exchange resins.

[0015] The invention provides high purity iron targets with 99.99 mass %or more in purity wherein a copper impurity content is 50 mass ppb orless.

[0016] In another aspect, the invention provides high purity irontargets wherein a residual resistivity ratio is 3000 or more, and acopper impurity content is 50 mass ppb or less.

[0017] In the high purity iron and the high purity iron targetsaccording to the invention, a concentration of copper is reduced to 50mass ppb or less to achieve high purification.

[0018] The method of manufacturing the high purity iron according to theinvention includes the steps of converting trivalent iron ions anddivalent copper ions respectively to divalent iron ions and monovalentcopper ions, and adjusting a concentration of hydrochloric acid. Thesesteps allow monovalent copper ions to be absorbed on the anion exchangeresins, and divalent iron ions not to be absorbed thereon. Thus thecopper can be separated easily and surely from the aqueous solution ofiron chloride.

[0019] Another method of manufacturing high purity iron according to theinvention includes the steps of converting trivalent iron ions in anaqueous solution of iron chloride to divalent iron ions and adjusting aconcentration of hydrochloric acid. These steps allow at least one ofimpurities selected from the group consisting of zinc, gallium, niobium,technetium, ruthenium, rhodium, palladium, silver, cadmium, indium, tin,antimony, tellurium, tantalum, tungsten, rhenium, osmium, iridium,platinum, gold, mercury, thallium, lead, and bismuth to be absorbed onthe anion exchange resins, and divalent iron ions not to be absorbedthereon. Thus the impurities can be separated easily and surely from theaqueous solution of iron chloride.

[0020] Other and further objects, features and advantages of theinvention will appear more fully from the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021]FIG. 1 is a flow chart illustrating a manufacturing process ofhigh purity iron and high purity iron targets according to oneembodiment of the invention.

[0022]FIG. 2 is a flow chart illustrating the manufacturing processfollowing FIG. 1.

[0023]FIG. 3 is a diagram explaining one step of the manufacturingprocess shown in FIG. 1.

[0024]FIG. 4 is a diagram explaining another step of the manufacturingprocesses shown in FIG. 1.

[0025]FIG. 5 is a graph illustrating changes of the concentrations ofmetal ions in the effluent of the anion exchange resins.

[0026]FIG. 6 is another graph illustrating changes of the concentrationsof metal ions in the effluent of the anion exchange resins.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] An embodiment of the present invention will be described indetail below with reference to the accompanying drawings.

[0028] In accordance with one embodiment of the invention, high purityiron and high purity iron targets have 99.99 mass % or more in purity,preferably 99.999 mass % or more, or the residual resistivity ratiosthereof are 3000 or more and copper impurity content thereof is 50 massppb or less.

[0029] The term “purity” (namely, chemical purity) used herein meansvalues obtained by one minus all concentrations of impurities possibleto be determined by using present analysis apparatus and methods (MinoruIsshiki, Koji Mimura, Bulletin of the Japan Institute of Metals, 31(1992), 880-887). For example, the values can be obtained by one minusthe concentrations of impurities of 70 or more elements determined byGlow Discharge Mass Spectroscopy. The concentrations of gas elementssuch as oxygen, nitrogen, and hydrogen, if required, can be determinedby appropriate methods such as a non-dispersive infrared absorptionmethod, a thermal conductivity method, and a heat conduction measurementof such gas elements separated with a column after being fused in aninert gas.

[0030] And, residual resistivity ratios provide one index showingpurities of highly purified metals, and as shown in the formula I, theresidual resistivity ratio is the ratio of resistivity at 298K toresistivity at 4.2K. The formula II shows a relationship betweenresistivity and resistance (electric resistance). Therefore, the formulaI expressing the residual resistivity ratio can be transformed into theformula III, and if volume. changes by temperature are negligible, theformula I can be approximated by the ratio of the resistance at 298K tothe resistance at 4.2K. It should be noted that iron is a ferromagneticmetal and factors such as geomagnetism, demagnetization conditions, andmagnetic fields by measurement currents can affect the resistancemeasurements. Thus, it is necessary to apply vertical magnetic fieldthat is preferably about 60 kA/m in measuring the resistance in order tosuppress these influences (Seiichi Takagi, Materia Japan, 33 (1994),6-10).

RRR=ρ _(298K)/ρ_(4.2K)  (I)

[0031] RRR; residual resistivity ratio

[0032] ρ_(298 K); resistivity at 298K (Ωm)

[0033] ρ_(4.2K); resistivity at 4.2K (Ωm)

ρ=R×(S/L)  (II)

[0034] ρ; resistivity (Ωm)

[0035] R; resistance (Ω)

[0036] S; cross-section area perpendicular to the direction of current(m²)

[0037] L; length (m) $\begin{matrix}{{RRR} = {\frac{R_{298K} \times \frac{S_{298K}}{L_{298K}}}{R_{4.2K} \times \frac{S_{4.2K}}{L_{4.2K}}} \approx \frac{R_{298K}}{R_{4.2K}}}} & ({III})\end{matrix}$

[0038] RRR; residual resistivity ratio

[0039] R_(298K), S_(298K), and L_(298K); respectively, resistance,cross-section area, length at 298K

[0040] R_(4.2K), S_(4.2K), and L_(4.2K); respectively resistance,cross-section area, length at 4.2K

[0041] The high purity iron and the high purity iron targets may be usedas materials of devices, for example, semiconductor devices, magneticrecording mediums, magnetic recording heads, and devices withenvironmental semiconductors. The term “environmental semiconductor”used herein means a semiconductor substance that exists abundantly onthe earth and consists of an eco-friendly material, for example, ironsilicide (FeSi₂) and calcium silicide (Ca₂Si) (See the website ofSociety of Kankyo Semiconductors(http://kan.engjm.saitama-u.ac.jp/SKS/index2.html)).

[0042] Such high purity iron and such high purity iron targets can bemanufactured as follows.

[0043]FIGS. 1 and 2 show the manufacturing process of the high purityiron according to the embodiment. First, the iron containing impuritiessuch as copper is dissolved in a hydrochloric acid solution in order toprepare an aqueous solution of iron chloride (FeCl₂ or FeCl₃) (StepS101). The concentration of the hydrochloric acid is adjusted in a rangeof 0.1 kmol/m³ to 6 kmol/m³.

[0044] And, as shown in FIG. 3, the aqueous solution of iron chloride Mis poured into a container 12 with a metal 11 such as iron. Then, theaqueous solution of iron chloride M is sufficiently contacted with themetal 11 by agitating with a device such as a stirrer 14, whileinjecting an inert gas 13 such as nitrogen gas (N₂) or argon gas (Ar)into the aqueous solution of iron chloride M (Step S102). Thus, thecopper contained in the aqueous solution of iron chloride M will reactwith the metal 11, for example, as shown in the following chemicalformula 1, converting the divalent copper ions to monovalent copper ionsor metallic copper. In addition, the iron contained in the aqueoussolution of iron chloride M will react with the metal 11, for example,as shown in the following chemical formula 2, converting the trivalentiron ions to divalent iron ions. It should be noted that the reaction ofthe chemical formula 1 may not completely proceed to the right-hand sideand a small amount of the monovalent copper ions may remain in theaqueous solution of iron chloride.

[CuCl₂]⁰+Fe (solid)→[FeCl₂]⁰+Cu (solid)  (1)

2[FeCl₆]³⁻+Fe (solid)→3[FeCl₄]²⁻  (2)

[0045] Dissolved oxygen can prevent reactions such as the above chemicalformulas 1 and 2. Therefore, injecting the inert gas 13 into the aqueoussolution of iron chloride M intends to remove oxygen dissolved in theaqueous solution of iron chloride M, in order to carry out thereactions. The inert gas 13 may be injected with agitating the aqueoussolution of iron chloride M containing the metal 11, or before the metal11 is added into the aqueous solution of iron chloride M.

[0046] Preferably, the metal 11 has large surface area such as powder,which can contact more effectively with the aqueous solution of ironchloride M and react sufficiently with the copper ions and iron ions.Substances other than iron can also be used for the metal 11. It ispreferred to use iron for the metal 11 in order to avoid otherimpurities from contaminating the aqueous solution of iron chloride M asmuch as possible.

[0047] The trivalent iron ions and divalent copper ions in the aqueoussolution of iron chloride M may be converted respectively to thedivalent iron ions and the monovalent copper ions by contacting with themetal 11 after adjusting the concentration of hydrochloric acid in theaqueous solution of iron chloride M as described above, or beforeadjusting the concentration of hydrochloric acid in the aqueous solutionof iron chloride.

[0048] Then, as shown in FIG. 4, a column 22 is filled up with the anionexchange resins 21, the aqueous solution of iron chloride M is fed intothe column 22 from a storage tank 23, and is contacted with the anionexchange resins 21 sufficiently (Step S103). The flow rate of theaqueous solution of iron chloride M is determined effectively to contactthe aqueous solution of iron chloride M with the anion exchange resins21 sufficiently, and is preferably 1 bed volume(s)/hour. The divalentcopper ions converted to the monovalent copper ions will be absorbed onthe anion exchange resins 21, and the trivalent iron ions converted todivalent iron ions will be eluted from the column 22 without beingabsorbed on the anion exchange resins 21. FIG. 5 shows changes of theconcentrations of metal ions in the effluent (elution curve). In FIG. 5,the abscissa represents the effluent volumes and the ordinate representsthe concentrations standardized by the maximum concentrations of themetal ions. As shown in FIG. 5, there is no range to which the peaks ofthe elution curves of the divalent iron ions and the monovalent copperions overlap, which shows that the copper can be completely separatedfrom the aqueous solution of iron chloride. That is, the aqueoussolution of iron chloride M from which copper is separated is collectedinto a recovery tank 24.

[0049] In addition, when at least one of impurities selected from thegroup consisting of zinc (Zn), gallium (Ga), niobium (Nb), technetium(Tc), ruthenium (Ru), rhodium (Rh), palladium (Pd), silver (Ag), cadmium(Cd), indium (In), tin (Sn), antimony (Sb), tellurium (Te), tantalum(Ta), tungsten (W), rhenium (Re), osmium (Os), iridium (Ir), platinum(Pt), gold (Au), mercury (Hg), thallium (Tl), lead (Pb), and bismuth(Bi) is contained in the aqueous solution of iron chloride M, as well aszinc and tin as shown in FIG. 5, in the Step S103, these impurities canbe absorbed on the anion exchange resins 21 with monovalent copper ionsand can be also separated from the aqueous solution of iron chloride M.

[0050] When at least one of impurities selected from the groupconsisting of lithium (Li), beryllium (Be), sodium (Na), magnesium (Mg),aluminum (Al), silicon (Si), phosphorus (P), potassium (K), calcium(Ca), scandium (Sc), titanium (Ti), vanadium (V), chromium (Cr),manganese (Mn), cobalt (Co), nickel (Ni), rubidium (Rb), strontium (Sr),yttrium (Y), zirconium (Zr), cesium (Cs), barium (Ba), lanthanoids,hafnium (Hf), francium (Fr), radium (Ra), and actinoids, is contained inthe aqueous solution of iron chloride M after separating the copper, anoxidizing agent such as a hydrogen peroxide solution as may be added tothe aqueous solution of iron chloride M to convert the divalent ironions to trivalent iron ions (Step S104). Or without such oxidationreaction the iron may be oxidized if the aqueous solution of ironchloride M is allowed to stand.

[0051] Then, the concentration of hydrochloric acid of aqueous solutionof iron chloride M is adjusted in a range of 2 kmol/m³ to 11 kmol/m³and, as shown in FIG. 4, the aqueous solution of iron chloride M issufficiently contacted with the anion exchange resins 21 (Step S105).Thus, the trivalent iron ions will be absorbed on the anion exchangeresins 21, and the impurities such as lithium, beryllium, sodium,magnesium, aluminum, silicon, phosphorus, potassium, calcium, scandium,titanium, vanadium, chromium, manganese, cobalt, nickel, rubidium,strontium, yttrium, zirconium, cesium, barium, lanthanoids, hafnium,francium, radium, and actinoids will not be absorbed on the anionexchange resins 21 and be eluted.

[0052]FIG. 6 shows changes of the concentrations of metal ions in theeffluent (elution curve). The changes of the concentrations of sometypical impurities, that is, aluminum, silicon, phosphorus, titanium,manganese, cobalt, and chromium, are shown in the FIG. 6 for comparisonwith the iron. In FIG. 6, the abscissa and the ordinate representrespectively the equivalents in the FIG. 5. As shown in FIG. 6, there isno range to which the peaks of the elution curves of the trivalent ironions and these impurities overlap, which shows that these impurities canbe completely separated from the aqueous solution of iron chloride.

[0053] Moreover, when at least one of impurities selected from the groupconsisting of zinc, gallium, niobium, molybdenum (Mo), technetium,ruthenium, rhodium, palladium, silver, cadmium, indium, tin, antimony,tellurium, tantalum, tungsten, rhenium, osmium, iridium, platinum, gold,mercury, thallium, lead, bismuth and polonium (Po) is contained in theaqueous solution of iron chloride M, these impurities can be absorbed onthe anion exchange resins 21 as well as the iron in the Step S105.

[0054] In such a case, after absorbing the iron on the anion exchangeresins 21, 0.1 kmol/m³ to 2 kmol/m³ of hydrochloric acid solution ispassed through the column 22 to elute the iron from the column filled upwith the anion exchange resins 21 and separate the iron from theimpurities absorbed on the anion exchange resins 21 such as zinc,gallium, niobium, molybdenum, technetium, ruthenium, rhodium, palladium,silver, cadmium, indium, tin, antimony, tellurium, tantalum, tungsten,rhenium, osmium, iridium, platinum, gold, mercury, thallium, lead,bismuth and polonium (Step S106). Changes of the concentrations of metalions in the effluent in the Step S106 are also shown in the FIG. 6.Especially, in the FIG. 6, the changes of the concentrations of sometypical impurities, that is, molybdenum and zinc are shown forcomparison with the iron. As shown in FIG. 6, there is no range to whichthe peaks of the elution curves of the trivalent iron ions and theseimpurities overlap, which shows that these impurities can be completelyseparated from the iron.

[0055] It should be noted that molybdenum and polonium will be mainlyseparated from the iron in the Step S106, because zinc, gallium,niobium, technetium, ruthenium, rhodium, palladium, silver, cadmium,indium, tin, antimony, tellurium, tantalum, tungsten, rhenium, osmium,iridium, platinum, gold, mercury, thallium, lead, and bismuth havealready been separated from the aqueous solution of iron chloride M withthe copper in the Step S103.

[0056] After eluting the iron, the obtained aqueous solution of ironchloride M is evaporated to dryness and is oxidized in order to obtainiron oxide (Step S107). Then, the obtained iron oxide is heated from 500K to less than 1800 K in a hydrogen atmosphere (Step S108). It ispreferred to heat to 1000 k or above for rapid reduction. Thus, the ironoxide will react as shown in the following chemical formula 3 to obtainiron.

3Fe₂O₃+H₂=2Fe₃O₄+H₂O

Fe₃O₄+H₂=3FeO+H₂O

Fe₃O₄+4H₂=3Fe+4H₂O

FeO+H₂=F+H₂O  (3)

[0057] After reacting of the iron oxide, the obtained iron is moltenwith plasma arc using a plasma generation gas containing activehydrogen, in order to remove at least one of impurities selected fromthe group consisting of oxygen, nitrogen, carbon (C), sulfur, halogen,alkaline metals, and alkaline-earth metals (Step S109). Thus, the stepsdescribed above can provide the high purity iron and the high purityiron targets according to the embodiment.

[0058] As described above, in the high purity iron and the high purityiron targets according to the invention, the contents of copper may bereduced to 50 mass ppb or less. Therefore, the high purity iron or theiron targets according to the invention may not be responsible for shortcircuit of devices such as semiconductor devices and can be applied tothe semiconductor devices for the enhancement of properties. Moreover,the high purity iron and the high purity iron targets can be used fordevices such as magnetic recording mediums and magnetic recording headsfor the enhancement of properties. In addition, the high purity iron andthe high purity iron targets used as materials of compoundsemiconductors such as iron silicide may not cause unwanted impuritylevel formed by small amounts of impurities responsible for propertydegradation and will provide good semiconductor properties.

[0059] Moreover, according to the method of manufacturing the highpurity iron, the trivalent iron ions and the divalent copper ions areconverted respectively to the divalent iron ions and the monovalentcopper ions, the concentration of the hydrochloric acid is adjusted from0.1 kmol/m³ to 6 kmol/m³, and the aqueous solution of iron chloride iscontacted with the anion exchange resins. Therefore, the copper may beseparated from the aqueous solution of iron chloride easily and the highpurity iron and the high purity iron targets with low concentrations ofcopper can be obtained easily and surely.

[0060] Furthermore, converting the trivalent iron ions to the divalentiron ions allows at least one of impurities selected from the groupconsisting of zinc, gallium, niobium, technetium, ruthenium, rhodium,palladium, silver, cadmium, indium, tin, antimony, tellurium, tantalum,tungsten, rhenium, osmium, iridium, platinum, gold, mercury, thallium,lead, and bismuth to be separated easily from the aqueous solution ofiron chloride M as well as the copper. Thus, the high purity iron andthe high purity iron targets can be obtained easily and surely.

[0061] The invention will be further described in detail by reference toFIGS. 1 to 6. In the following examples, the same reference numbers andsigns will be used for equivalents of the substances in the aboveembodiments.

EXAMPLE

[0062] First, in order to prepare an aqueous solution of iron chloride(FeCl₃) M, scrap iron used as a material was dissolved into 2 kmol/m³ ofhydrochloric acid solution until the concentration of the iron reached0.179 kmol/m³ (10 g/dm³) (Step S101). Then, as shown in FIG. 3, powderediron 11 was added to the aqueous solution of iron chloride M, and inertgas was injected into the solution M with agitating to convert divalentcopper ions and trivalent iron ions respectively to monovalent copperions and divalent iron ions (Step S102). Then, as shown in FIG. 4, theaqueous solution of iron chloride M was contacted with the anionexchange resins 21 to absorb the monovalent copper ions and separate thecopper ions from the aqueous solution of iron chloride M (Step S103).

[0063] After separating the copper, a hydrogen peroxide solution wasadded to the aqueous solution of iron chloride M to convert the divalentiron ions to trivalent iron ions (Step S104). Then, the concentration ofhydrochloric acid of the aqueous solution of iron chloride M wasadjusted to 5 kmol/m³, and the aqueous solution of iron chloride M wascontacted with the anion exchange resins 21 to absorb the trivalent ironions and separate impurities such as lithium (Step S105). Then, the ironwas eluted from the column filled up with the anion exchange resins 21with 1 kmol/m³ of hydrochloric acid solution to separate impurities suchas molybdenum (Step S106).

[0064] After eluting the iron from the column filled up with the anionexchange resins 21, the obtained aqueous solution of iron chloride M wasevaporated to dryness and oxidized to obtain iron oxide (Step S107).And, the obtained iron oxide was heated to 1073 K (800° C.) in ahydrogen atmosphere to obtain iron (Step S108). The iron obtained in theStep S108 was molten with plasma arc containing active hydrogen toremove impurities such as oxygen (Step S109) to obtain high purity iron.

[0065] Quantities of purities contained in the obtained high purity ironwere determined by Glow Discharge Mass Spectroscopy, and a value ofpurity and residual resistivity ratio was calculated. Table 1 shows theresults. As shown in Table 1, the copper concentration was as very lowas 50 mass ppb or less, and the value of purity was as very high as99.9997%, and the residual resistivity ratio was as very high as 5500.TABLE 1 Concentration Concentration Concentration Element (mass ppm)Element (mass ppm) Element (mass ppm) Concentration Al  0.380 Co  0.035Rh <0.010 of impurities As <0.050 Ga  0.050 Ru <0.010 B <0.010 Hf <0.010Sb <0.020 Ba <0.010 In <0.020 Si  0.060 Be <0.010 K  0.015 Sn  0.270 Bi 0.012 Li <0.010 Th  0.001 Ca  0.110 Mg <0.010 Ti  0.150 Cd  0.120 Mn<0.050 U  0.002 Cl <0.050 Mo <0.050 V  1.000 Cr <0.020 Na <0.010 Zn 0.050 Cu <0.020 Ni <0.020 Zr  0.016 F <0.050 P  0.740 Pb  0.014 Purity99.9997% Residual 5500 resistivity ratio

[0066] It is found that due to converting trivalent iron ions anddivalent copper ions respectively to divalent iron ions and monovalentcopper ions and adjusting the concentration of hydrochloric acid from0.1 kmol/m³ to 6 kmol/m³, copper could be easily separated from theaqueous solution of iron chloride, and the high purity iron having theconcentration of copper reduced to 50 mass ppb or less could be obtainedeasily.

[0067] As described above, the invention is explained by the embodimentsand examples. These embodiments and examples are not meant to limit thescope of the invention and variations within the concepts of theinvention are apparent. For example, as described in the embodiments andexamples, after converting the trivalent iron ions and the divalentcopper ions respectively to the divalent iron ions and the monovalentcopper ions, adjusting the concentrations of hydrochloric acid and theaqueous solution of iron chloride, and contacting the aqueous solutionof iron chloride with the anion exchange resins, the copper may beabsorbed on the anion exchange resins and be separated from the iron.After adjusting the valencies of iron and copper and absorbing iron andcopper on the anion exchange resins, iron may be eluted with 0.1 kmol/m³to 6 kmol/m³ of hydrochloric acid solution in order to separate thecopper from the aqueous solution of iron chloride.

[0068] Moreover, impurities other than copper may be removed by themethods as described in the above embodiments and examples, or by otherconventional methods. Furthermore, the copper may be separated as wellas the impurities such as zinc from the aqueous solution of ironchloride after converting the trivalent iron ions to divalent iron ionsas described above, or may be separated by other methods.

[0069] As described above, in the high purity iron and the high purityiron targets according to the invention, the contents of copper whichcauses influences such as a short circuit may be reduced to 50 mass ppbor less. Therefore, the high purity iron or the high purity iron targetsaccording to the invention applied to semiconductor devices may not beresponsible for short circuit of devices such as semiconductor devicesand can provide the enhancement of properties of the semiconductordevices. Moreover, the high purity iron and the high purity iron targetscan use for devices such as magnetic recording mediums and magneticrecording heads for the enhancement of properties. In addition, the highpurity iron and the high purity iron targets used as materials ofcompound semiconductors such as iron silicide may not cause unwantedimpurity level formed by small amounts of impurities responsible forproperty degradation and will provide good semiconductor properties.

[0070] Moreover, according to the method of manufacturing the highpurity iron of the invention, the trivalent iron ions and the divalentcopper ions are converted respectively to the divalent iron ions and themonovalent copper ions and the concentration of the hydrochloric acid isadjusted from 0.1 kmol/m³ to 6 kmol/m³. Therefore, the copper may beabsorbed on the anion exchange resins and be separated from the aqueoussolution of iron chloride easily. In addition, the high purity iron andthe high purity iron targets with low concentration of copper can beobtained easily and surely.

[0071] Furthermore, in another aspect, according to the method ofmanufacturing the high purity iron of the invention, the trivalent ironions are converted to the divalent iron ions and the concentration ofthe hydrochloric acid is adjusted from 0.1 kmol/m³ to 6 kmol/m³.Therefore, the impurities such as zinc may be absorbed on the anionexchange resins and be separated from the aqueous solution of ironchloride easily. In addition, the high purity iron and the high purityiron targets can be obtained easily and surely.

[0072] Obviously many modifications and variation of the presentinvention are possible in the light of the above teachings. It istherefore to be understood that within the scope of the appended claimsthe invention may be practiced otherwise than as specifically described.

What is claimed is:
 1. High purity iron with 99.99 mass % or more inpurity wherein a copper impurity content is 50 mass ppb or less.
 2. Highpurity iron wherein a residual resistivity ratio thereof is 3000 ormore, and a copper impurity content is 50 mass ppb or less.
 3. A methodof manufacturing high purity iron comprising the steps of; convertingtrivalent iron ions and impurity divalent copper ions contained in anaqueous solution of iron chloride respectively to divalent iron ions andmonovalent copper ions; adjusting a concentration of hydrochloric acidin a range of 0.1 kmol/m³ to 6 kmol/m³; and separating the monovalentcopper ions from the aqueous solution of iron chloride by using ionexchange resins.
 4. A method of manufacturing high purity iron accordingto claim 3, comprising the steps of; converting trivalent iron ions andimpurity divalent copper ions contained in an aqueous solution of ironchloride respectively to divalent iron ions and monovalent copper ions;adjusting a concentration of hydrochloric acid in the aqueous solutionof iron chloride in a range of 0.1 kmol/m³ to 6 kmol/m³; and contactingthe aqueous solution of iron chloride with anion exchange resins toseparate the monovalent copper ions from the aqueous solution of ironchloride after the steps of converting the trivalent iron ions and thedivalent copper ions respectively to the divalent iron ions and themonovalent copper ions and adjusting the concentration of hydrochloricacid.
 5. A method of manufacturing high purity iron according to claim3, wherein the converting step comprises the steps of; injecting aninert gas into the aqueous solution of iron chloride; and convertingtrivalent iron ions and divalent copper ions contained in an aqueoussolution of iron chloride respectively to divalent iron ions andmonovalent copper ions by contacting the aqueous solution of ironchloride with iron.
 6. A method of manufacturing high purity ironaccording to claim 3, wherein at least one of impurities selected fromthe group consisting of zinc, gallium, niobium, technetium, ruthenium,rhodium, palladium, silver, cadmium, indium, tin, antimony, tellurium,tantalum, tungsten, rhenium, osmium, iridium, platinum, gold, mercury,thallium, lead, and bismuth is separated from the aqueous solution ofiron chloride in the step of separating the copper.
 7. A method ofmanufacturing high purity iron according to claim 3, further comprisingthe steps of; adjusting the concentration of hydrochloric acid in theaqueous solution of iron chloride in a range of 2 kmol/m³ to 11 kmol/m³;contacting the aqueous solution of iron chloride with the anion exchangeresins to absorb the iron of trivalent ions thereon and separate atleast one of impurities selected from the group consisting of lithium,beryllium, sodium, magnesium, aluminum, silicon, phosphorus, potassium,calcium, scandium, titanium, vanadium, chromium, manganese, cobalt,nickel, rubidium, strontium, yttrium, zirconium, cesium, barium,lanthanoids, hafnium, francium, radium and actinoids contained in theaqueous solution of iron chloride, from the aqueous solution of ironchloride; and eluting the iron from the anion exchange resins with ahydrochloric acid solution.
 8. A method of manufacturing high purityiron according to claim 7, wherein a hydrochloric acid solution having aconcentration of 0.1 kmol/m³ to 2 kmol/m³ is used for eluting the ironfrom the anion exchange resins in order to separate the iron from atleast one of impurities selected from the group consisting of zinc,gallium, niobium, molybdenum, technetium, ruthenium, rhodium, palladium,silver, cadmium, indium, tin, antimony, tellurium, tantalum, tungsten,rhenium, osmium, iridium, platinum, gold, mercury, thallium, lead,bismuth and polonium absorbed on the anion exchange resins.
 9. A methodof manufacturing high purity iron according to claim 3, furthercomprising the steps of; obtaining iron oxide from the aqueous solutionof iron chloride which the impurity copper are separated therefrom; andheating the iron oxide in a hydrogen atmosphere to obtain iron.
 10. Amethod of manufacturing high purity iron according to claim 9, furthercomprising the step of melting the iron obtained in the heating stepwith plasma arc using a plasma generation gas containing active hydrogenin order to remove at least one of impurities selected from the groupconsisting of oxygen, nitrogen, carbon, sulfur, halogen, alkalinemetals, and alkaline-earth metals.
 11. A method of manufacturing highpurity iron comprising the steps of; converting trivalent iron ions inan aqueous solution of iron chloride to divalent iron ions; adjusting aconcentration of hydrochloric acid in a range of 0.1 kmol/m³ to 6kmol/m³; and separating at least one of impurities selected from thegroup consisting of zinc, gallium, niobium, technetium, ruthenium,rhodium, palladium, silver, cadmium, indium, tin, antimony, tellurium,tantalum, tungsten, rhenium, osmium, iridium, platinum, gold, mercury,thallium, lead, and bismuth from the aqueous solution of iron chlorideby using the anion exchange resins.
 12. High purity iron targets with99.99 mass % or more in purity wherein a copper impurity content is 50mass ppb or less.
 13. High purity iron targets wherein a residualresistivity ratio is 3000 or more, and a copper impurity content is 50mass ppb or less.